Eccentric valve device and control method thereof

Abstract

To provide an eccentric valve device which can surely detect or predict seat leakage even in a short opening / closing time, in an eccentric valve including a double-eccentric valve.SOLUTION: An eccentric valve device 1 comprises: a valve box 21; a seat member 23; a valve body 22 arranged in the valve box 21 so as to be turnable, and blocking a flow passage by being push-pressed to the seat member 23; a valve drive part 3 for turning the valve body 22; and a control part 4 for controlling the drive of the valve drive part 3. The valve body 22 has a structure in which the valve body does not contact with the seat member 23 in a full-opened state, and contacts with the seat member 23 in a full-closed state. The control part 4 has a speed control part for changing a turning speed of the valve body 22 in a process in which the valve body 22 turns to the full-closed state from the full-open state, and a leakage determination part for determining the presence or absence of leakage between the seat member 23 and the valve body 22 on the basis of a drive parameter of the valve drive part 3.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an eccentric valve device and a control method thereof. [Background technology]

[0002] Conventionally, piping systems constituting production processes in factories and the like incorporate valve devices to control the flow of various gases, liquids, powders, and mixtures thereof (hereinafter collectively referred to as fluids). The flow path in the piping is blocked or opened by opening and closing the valve of the valve device. For example, a valve device equipped with an automatic operation function can open and close the valve without manual operation.

[0003] In general, a valve device with an automatic operation function comprises a substantially cylindrical valve box having an opening communicating with a flow path, a ring-shaped seat member attached around the opening inside the valve box, a valve body that is rotatably mounted within the valve box and blocks the flow path when pressed against the seat member, a valve drive unit that rotates the valve body, and a control unit that controls the drive of the valve drive unit.

[0004] There are various types of valves known for use in valve devices, including double eccentric valves and single eccentric valves such as ball valves. A double eccentric valve has an eccentric structure in which the rotation axis of the valve body is eccentric with respect to the axis of the seat member, and the valve body and the seat member are not in contact when the flow path is open, and only come into contact near the position where the valve body closes the flow path (see Patent Document 1). On the other hand, in a ball valve, the valve body and the seat member are always in contact with each other, and the valve body opens and closes when pressed against the seat member. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-48856 A Summary of the Invention [Problem to be solved by the invention]

[0006] In an eccentric valve, when the valve body is in the fully closed state, the valve body crushes the seat member, and the contact surface of the valve body with the seat member receives a repulsive force. As a result, the two come into close contact and the flow of fluid is blocked. However, even in the fully closed state, so-called seat leakage may occur, in which fluid flows between the valve body and the seat member from upstream to downstream. Seat leakage is undesirable because it changes the amount of fluid flowing as a material and may adversely affect the quality of the product. Therefore, it is required to keep the amount of fluid leakage within an allowable range when the valve body is fully closed.

[0007] Generally, there are two types of seat leakage: one caused by foreign matter getting caught between the seat member and the valve body, and the other caused by the sagging or wear of the seat member. The former type of seat leakage occurs when solid foreign matter adheres to the contact surface between the valve body and the seat member, and is often a temporary leak unless the seat member is permanently damaged. On the other hand, the latter type of seat leakage occurs due to deterioration of the seat member over time, and once leakage occurs, it continues to occur, which may have a negative impact on, for example, product quality.

[0008] In addition, since sheet leakage due to sagging or wear is an event that occurs inside the valve device, it is difficult to immediately detect the occurrence from the outside. In particular, valve devices equipped with an automatic operation function are often installed in narrow places, remote places, or special atmospheric environments where manual inspection is not possible. Therefore, sheet leakage is often discovered some time after it occurs, which may result in energy loss, resource loss, and reduced yield. For example, a method for detecting sheet leakage may be considered in which various sensors such as a flow rate sensor and a vibration sensor are installed and the leakage is detected based on the output from the sensor. However, this method has problems such as the expense of installing the sensors and the difficulty of setting a threshold value for determining the occurrence of sheet leakage. Therefore, it is desired to be able to detect sheet leakage due to sagging or wear immediately after its occurrence by an easy means, or to predict it in advance.

[0009] In addition, it is desirable for a valve device to be able to immediately shut off a flow path when a request to shut off the flow path is made. However, it takes a certain amount of time for the valve element to change from a fully open state to a fully closed state, and the flow of fluid after the request to shut off is wasted in the production process. For this reason, it is desirable for the opening and closing time of the valve element to be short.

[0010] The present invention has been made in consideration of the above circumstances, and has an object to provide an eccentric valve device and a control method thereof that can reliably detect or predict sheet leakage in an eccentric valve, including a double eccentric valve, even when the opening and closing time is short. [Means for solving the problem]

[0011] The eccentric valve device of the present invention is an eccentric valve device that controls the blocking or opening of a flow path in a pipe, the eccentric valve device includes a substantially cylindrical valve box having an opening communicating with the flow path, a ring-shaped seat member attached around the opening in the valve box, a valve body that is rotatably provided in the valve box and blocks the flow path when pressed against the seat member, a valve drive unit that rotates the valve body, and a control unit that controls the drive of the valve drive unit, the valve body being structured so that it does not contact the seat member in a fully open state and contacts the seat member in a fully closed state, the control unit being characterized in that it includes a speed control unit that changes the rotation speed of the valve body in the process of rotating from the fully open state to the fully closed state, and a leak determination unit that determines the presence or absence of leakage between the seat member and the valve body based on the drive parameters of the valve drive unit. Here, "determining the presence or absence of leakage" includes not only determining that a leakage has actually occurred, but also determining a sign of leakage.

[0012] In the present invention, it is preferable that the speed control section rotates the valve element from the fully open state at a first speed, and then changes the rotation speed to a second speed slower than the first speed to rotate the valve element to the fully closed state.

[0013] In the present invention, the speed control unit preferably rotates the valve element from a predetermined position where the valve element is close to the seat member to the fully closed state at the second speed. Here, the "predetermined position close to the seat member" refers to a position where the valve element does not contact the seat member and where the gap between the valve element and the seat member can be narrowed to increase the flow rate of the fluid to a level where foreign matter adhering to the valve element and the seat member can be blown away.

[0014] In the present invention, it is more preferable that the control unit has a torque calculation unit that calculates a drive torque of the valve drive unit based on the drive parameters, and the leak determination unit determines that a leak has occurred between the seat member and the valve body when the drive torque is smaller than a predetermined threshold value while the valve body is rotating at the second speed.

[0015] Furthermore, in the present invention, it is more preferable that the time required for the valve element to change from a fully open state to a fully closed state is within 3.0 seconds.

[0016] In the present invention, the valve drive portion may be an electric motor that is capable of rotating the valve element by inertia even after the supply of current thereto is stopped.

[0017] The control method for an eccentric valve device of the present invention is a control method for an eccentric valve device that controls the blocking or opening of a flow path in a pipe, the eccentric valve device comprising: a substantially cylindrical valve box having an opening communicating with the flow path; a ring-shaped seat member attached around the opening inside the valve box; a valve body that is rotatably provided inside the valve box and blocks the flow path when pressed against the seat member; and a valve drive unit that rotates the valve body, wherein the valve body does not contact the seat member in a fully open state and contacts the seat member in a fully closed state. The control method is characterized by comprising the steps of: rotating the valve body at a first speed in the process of rotating the valve body from the fully open state to the fully closed state; and determining the presence or absence of leakage between the seat member and the valve body based on drive parameters of the valve drive unit while rotating the valve body at a second speed slower than the first speed. Effect of the Invention

[0018] By configuring the eccentric valve device and the control method thereof according to the present invention in this way, it is possible to reliably detect or predict seat leakage even with a short opening and closing time. [Brief description of the drawings]

[0019] [Figure 1] 1 is an explanatory diagram showing a schematic configuration of an entire eccentric valve device according to the present invention; [Diagram 2] FIG. 2 is an enlarged cross-sectional view of the valve mechanism portion of FIG. [Diagram 3] FIG. 4 is a cross-sectional view showing a valve body in a fully open state. [Figure 4] FIG. 4 is a cross-sectional view showing a valve body in a fully closed state. [Diagram 5] 13 is a diagram showing a change in shaft torque when the valve body transitions from a fully closed state to a fully closed state. FIG. [Figure 6] 13 is a diagram showing a change in shaft torque when the valve body transitions from a fully closed state to a fully closed state. FIG. [Figure 7]13 is a diagram showing a change in shaft torque when the valve body transitions from a fully closed state to a fully closed state. FIG. [Figure 8] 4 is a graph showing a ratio of the shaft torque at the timing when the power supply to the motor is stopped to the peak value of the shaft torque. [Figure 9] FIG. 2 is a block diagram of an eccentric valve device according to the present invention. [Figure 10] 11A and 11B are diagrams illustrating an example of a position where the rotation speed of the valve body is switched. [Figure 11] FIG. 13 is a diagram showing changes in driving torque of a new sheet member and a worn sheet member. [Figure 12] FIG. 13 is a diagram showing changes in driving torque of a new sheet member and a worn sheet member. [Figure 13] 10 is a flowchart showing a processing procedure for detecting a sheet leakage. [Figure 14] FIG. 11 is a diagram showing a relationship between a calculated driving torque and a threshold value. [Figure 15] 6 is an example of a timing chart when a valve body transitions from a fully open state to a fully closed state. [Figure 16] 13 is another example of a timing chart when the valve body transitions from a fully open state to a fully closed state. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Fig. 1 is an explanatory diagram showing a schematic configuration of the entire eccentric valve device according to the present invention, and Fig. 2 is an enlarged cross-sectional view of a valve mechanism part of Fig. 1. Note that Fig. 1 shows a cross-sectional view of a part of the eccentric valve device. The eccentric valve device 1 shown in Fig. 1 is a device that is disposed in the middle of a flow path in a pipe through which a fluid flows, and controls blocking and / or opening of the flow path.

[0021] 1, the eccentric valve device 1 includes a valve mechanism unit 2 having a valve disc 22, a valve drive unit 3 that drives the valve mechanism unit 2, and a control unit 4 that controls the drive of the valve drive unit 3. The valve mechanism unit 2 and the valve drive unit 3 are connected by a valve rod 35, and the drive of the valve drive unit 3 can be transmitted to the valve mechanism unit 2. The eccentric valve device 1 has a function of being able to hold the attitude of the valve disc 22 in a fully open position, a fully closed position, or any other position (for example, a position immediately before fully closed).

[0022] The control unit 4 is mainly composed of a microcomputer including a well-known CPU, ROM, RAM, etc. In Figures 1 and 9, the control unit 4 is illustrated separately from the valve driving unit 3 for convenience, but the valve driving unit 3 also has a built-in microcomputer, and all or part of the functions of the control unit 4 described below may be provided by the microcomputer in the valve driving unit 3.

[0023] The valve mechanism 2 includes a substantially cylindrical valve box 21, a valve element 22 rotatably provided within the valve box 21, a ring-shaped seat member 23 attached within the valve box 21, and a support member 24 that supports the seat member 23. The valve mechanism 2 is installed midway through a piping for a fluid, and pipes (not shown) are connected to the upstream and downstream sides of the valve box 21. The fluid flows in the direction of the arrow in Fig. 1. By rotating the valve element 22 in the valve mechanism 2, the flow path within the valve box 21 is blocked or opened, and the flow of the fluid from the upstream side to the downstream side can be blocked or opened.

[0024] As shown in FIG. 2, the valve box 21 has an opening 211 that communicates the upstream flow path and the downstream flow path. Around the opening 211, a step 214 is formed that protrudes radially inward so that the inner circumferential surface of the valve box 21 has a reduced diameter, and the seat member 23 is attached to the step 214. The seat member 23 is supported by a support member 24 inserted from the upstream end of the valve box 21. The upper part of the valve box 21 is formed with a mounting hole 212 that penetrates the inner circumferential surface and the outer circumferential surface and into which the valve rod 35 is inserted. The mounting hole 212 is formed in a direction perpendicular to the axial direction of the valve box 21, and the valve rod 35 is rotatably inserted. In addition, a pin groove 213 into which the pin 25 fits is formed in the lower part of the valve box 21.

[0025] In the valve box 21, the valve element 22 is connected to the end of the valve rod 35, and the valve element 22 rotates with the rotation of the valve rod 35. The rotation axis of the valve rod 35 and the rotation axis of the valve element 22 are aligned. Note that Fig. 2 shows a fully closed state in which the valve element 22 blocks the opening 211.

[0026] The valve body 22 has a substantially disk-shaped valve portion 221 and support portions 222 and 223. The upstream end face of the valve portion 221 constitutes a seal surface and is formed by a flat surface at the center of the disk and a curved surface at the peripheral edge of the disk. The curved surface is formed in a convex shape toward the upstream side. The support portion 222 is connected to the valve rod 35, and the support portion 223 is connected to the pin 25. The valve body 22 is formed from a metal material such as stainless steel, a resin material, or the like.

[0027] The seat member 23 has a hollow circular seat ring 231 and a rubber ring 232. The surface of the seat ring 231 facing the valve body 22 constitutes a sealing surface. A groove is formed on the back side of the sealing surface of the seat ring 231, and the rubber ring 232 is fitted into the groove. The seat ring 231 is made of a resin such as polytetrafluoroethylene resin. This resin may be mixed with a fibrous reinforcing material such as carbon fiber or glass fiber. For the rubber ring 232, for example, fluororubber such as tetrafluoroethylene-perfluoromethylvinylether rubber (FFKM) or nitrile butadiene rubber (NBR) can be used. In the fully closed state as shown in FIG. 2, the valve portion 221 of the valve body 22 is pressed against the seat member 23, so that the sealing surface of the valve body 22 is in close contact with the sealing surface of the valve body 22.

[0028] Next, the operation of the valve mechanism 2 will be described with reference to Figures 3 and 4. Figures 3 and 4 are partial cross-sectional views of the valve mechanism in Figure 2, viewed from the valve rod side. As shown in each figure, the valve body 22 has a double eccentric structure. Specifically, the rotation axis O of the valve body 22 is eccentric by a distance Y with respect to the axis of the seat ring 231, and the rotation axis O of the valve body 22 is eccentric by a distance X with respect to the seal surface of the seat ring 231.

[0029] FIG. 3 shows the fully open state of the valve body 22, where the valve portion 221 of the valve body 22 faces a direction perpendicular to the flow path. At this time, the valve body 22 is not in contact with the sheet member 23. From this fully open state, the valve body 22 rotates so that the valve portion 221 faces the upstream side of the flow path. The valve body 22 rotates at a rotation angle θ of 0 degrees to 90 degrees, where the fully open state is 0 degrees and the fully closed state is 90 degrees. FIG. 4 shows the fully closed state of the valve body 22, where the valve portion 221 of the valve body 22 faces the upstream direction of the flow path. The flow path is blocked by the valve body 22 coming into close contact with the sheet member 23. The opening and closing speed of the valve body 22 can be set appropriately, and generally, the time required from the fully open state to the fully closed state is 1 second or more.

[0030] In the fully closed state of FIG. 4, the seat member 23 is elastically deformed by being pressed against the valve body 22. The amount of deformation (deformation margin) of the seat member 23 is generally about 1 / 500 to 1 / 1000 of the cross-sectional width of the seat member 23. In the case of an eccentric valve, the seat member is repeatedly deformed every time the valve body opens and closes. The seat member is scraped or worn down (permanent set) in approximately proportion to the number of times the valve body is opened and closed, and the amount of deformation (repulsion force) of the seat member decreases, and ultimately there is a risk of seat leakage occurring. The present invention uses the drive parameters of the valve drive unit to detect or predict a decrease in the repulsion force of the seat member over time as seat leakage.

[0031] First, the transition of the shaft torque when the valve body is closed will be described. FIG. 5 shows the transition of the shaft torque, the transition of the motor current, and the brake state when the valve body rotates from the fully open state (at 0 seconds) to the fully closed state (at 8 seconds). During the valve closing operation, the valve drive unit energizes the motor unit to rotate the output shaft and rotate the valve body. Then, at a predetermined timing, the motor unit is de-energized and the brake is activated at the same time to fully close the valve body. The valve drive unit is, for example, an electric motor (brushless motor, etc.) that rotates the valve body by inertial force even after de-energization. In this case, the timing of de-energization and activation of the brake is set according to the rotation speed of the valve body so that the load due to the inertial force is not excessively applied to the seat member.

[0032] In FIG. 5, the shaft torque (dashed line) is a value detected by a torque sensor attached to the output shaft of the motor. The torque sensor has a strain gauge and generates a detection signal corresponding to the shaft torque generated on the output shaft of the motor. The motor current (dotted line) is a motor current calculated, for example, from the voltage value across a shunt resistor in the motor circuit. Note that in FIG. 5, the motor current gently decreases after the brake is activated, that is, after the current to the motor is cut off, but this is due to the influence of the measurement method, and in reality, the current becomes zero immediately after the current is cut off. Note that the brake state (solid line) indicates the brake operation off and on states.

[0033] FIG. 5 shows the case where the time required for the valve disc to change from the fully open state to the fully closed state (opening / closing time) is 8.0 seconds. In this test, the rotation speed of the valve disc is kept constant by energizing the motor unit. As shown in FIG. 5, the shaft torque is almost constant from the start of the valve disc closing operation until 7 seconds before, and then starts to increase around 7 seconds, and continues to increase until it reaches 8 seconds when the valve disc is in the fully closed state. This shaft torque transition is based on the operation in which the valve disc contacts the seat member as the valve opening operation progresses and further pushes the seat member. Also, in FIG. 5, the motor current shows a temporary increase immediately after the start, but then shows a transition in which it increases just before the fully closed state, similar to the shaft torque transition. In other words, the motor current can be said to reflect the driving torque of the valve disc during the valve closing operation, and it is considered that this can be used to detect and predict seat leakage.

[0034] In the example of Fig. 5, if the shaft torque at the peak (at 8.0 seconds) is taken as 100%, the ratio of the shaft torque at the time the brake is applied is approximately 100%. In other words, in this case, the motor section is energized until the valve body is almost fully closed. Therefore, seat leakage can be detected by using the motor current for the entire section where the valve body is pressing the seat member.

[0035] Next, Fig. 6 and Fig. 7 show examples of shaft torque transition etc. when the opening and closing time of the valve disc is made shorter than 8.0 seconds. Fig. 6(a) shows the case of 4.0 seconds, Fig. 6(b) shows 3.0 seconds, Fig. 7(a) shows 2.0 seconds, and Fig. 7(b) shows 1.0 second.

[0036] As shown in FIG. 6 and FIG. 7, the shorter the opening / closing time, the earlier the timing of braking with respect to the target time (for example, 4.0 seconds after the start of the valve closing operation in the case of an opening / closing time of 4.0 seconds). In other words, the shorter the opening / closing time, the earlier the timing of stopping the power supply to the motor. This is because the shorter the opening / closing time of the valve disc, the faster the rotation speed of the valve disc, and the longer the time the valve disc moves by inertia after the power supply is stopped. For example, in the case of an opening / closing time of 8.0 seconds, the power supply time is 100%, whereas in the case of an opening / closing time of 4.0 seconds, the power supply time is 99.4%, in the case of an opening / closing time of 3.0 seconds, the power supply time is 99.3%, in the case of an opening / closing time of 2.0 seconds, the power supply time is 97.8%, and in the case of an opening / closing time of 1.0 second, the power supply time is 91.8%. As shown in FIG. 6 and FIG. 7, the earlier the timing of stopping the power supply to the motor, the shorter the section in which the driving parameters can be measured is with respect to the entire section (100%).

[0037] FIG. 8 is a graph showing the ratio of the shaft torque at the timing when the power supply to the motor is stopped to the peak value of the shaft torque. Since the transition of the shaft torque reflects the transition of the driving torque while the motor is energized, the graph in FIG. 8 can be said to show the ratio of the driving parameter that can be measured to the peak value. As shown in FIG. 8, when the opening and closing time is 8.0 seconds, the measurable driving parameter is about 100%, whereas when the opening and closing time is 4.0 seconds, it is about 94%, when the opening and closing time is 3.0 seconds, it is about 92%, when the opening and closing time is 2.0 seconds, it is about 81%, and when the opening and closing time is 1.0 seconds, it is about 35%. In other words, when the opening and closing time is within 4.0 seconds, the supply of power to the motor is stopped before the shaft torque reaches the peak value, so that the driving parameter cannot be measured in the entire section until the shaft torque reaches the peak value.

[0038] In contrast, the eccentric valve device of the present invention is characterized by having a speed control section that changes the rotation speed of the valve disc in the process of rotating from a fully open state to a fully closed state, and a leakage determination section that determines the presence or absence of leakage between the seat member and the valve disc based on the drive parameters of the valve drive section. Specifically, a period in which the valve disc is rotated quickly by the speed control section is combined with a period in which the valve disc is rotated slowly thereafter. This makes it possible to shorten the overall opening and closing time while bringing the timing of stopping the power supply to the motor as close as possible to the fully closed state, that is, bringing the section in which the drive parameters can be measured as close as possible to the entire section, so that the increase in drive torque can be sufficiently determined by the drive parameters.

[0039] FIG. 9 is a block diagram showing an example of an eccentric valve device according to the present invention. The eccentric valve device 1 includes a valve mechanism unit 2, a valve driving unit 3, and a control unit 4, and the specific configuration of the valve mechanism unit 2 is as described above. The eccentric valve device 1 also includes sensors 51, 52, and 53 for detecting drive parameters, and each sensor is connected to the control unit 4. The detection results of each sensor are input to the control unit 4 at any time, and are configured to be continuously detected and stored during opening and closing operations. The control unit 4 also has various calculation functions. In the present invention, the drive parameters are parameters that indicate the drive state of the valve driving unit 3, and include, for example, the motor rotation speed, motor current value, motor voltage value, drive torque, and rotation angle θ of the motor unit 33. In the present invention, the drive parameters of the valve driving unit 3 are used to detect sheet leakage, so that separate sensors such as a torque sensor, a flow rate sensor, and a vibration sensor are not essential, and sheet leakage can be detected by a simple means of monitoring the motor rotation speed and current value.

[0040] The valve drive unit 3 includes a power supply circuit unit 31, a motor circuit unit 32, a motor unit 33, a reducer (gear box) 34, a valve rod 35, and a current sensor 53. The motor circuit unit 32 is connected to the power supply circuit unit 31, and adjusts the current flowing to the motor unit 33 based on a control signal from the control unit 4. The motor unit 33 is made of a brushless motor, and rotates an output shaft based on the current flowing from the motor circuit unit 32. In the configuration of FIG. 1, the rotation speed of the output shaft is reduced by the reducer 34 to rotate the valve rod 35.

[0041] 9, the control unit 4 has a speed control unit 41, a torque calculation unit 42, and a leakage determination unit 43. The processing in each unit is mainly executed when the valve body transitions from a fully open state to a fully closed state.

[0042] The speed control unit 41 changes the rotation speed of the valve disc at a predetermined timing in the process of the valve disc rotating from the fully open state to the fully closed state. Specifically, after rotating the valve disc from the fully open state at a first speed, the rotation speed is changed to a second speed slower than the first speed to rotate the valve disc to the fully closed state. The second speed is set to, for example, 1 / 8 to 1 / 3 of the first speed. Here, the timing of switching from the first speed to the second speed is based on the fact that the valve disc has rotated to a predetermined position. The fact that the valve disc has rotated to the predetermined position is determined by a position determination unit in the control unit 4 based on the rotation angle detected by an angle sensor 52 such as an encoder.

[0043] The above-mentioned predetermined position is preferably a predetermined position close to the seat member. The predetermined position close to the seat member is, for example, as shown in FIG. 10, a position where the valve body 22 does not contact the seat member 23, where the gap between the valve body 22 and the seat member 23 is narrowed, and where the flow rate of the fluid can be increased to a degree that blows away foreign matter attached to the valve body 22 and the seat member 23. In this case, when the rotation angle θ becomes, for example, 60 degrees or 70 degrees, the first speed is switched to the second speed. By switching at a predetermined position close to the seat member, the frictional force generated by the subsequent contact between the valve part 221 and the seat ring 231 becomes a pure frictional force that is not influenced by foreign matter, so that a decrease in sealing performance due to sagging or wear can be detected separately from a decrease in sealing performance due to the ingress of foreign matter.

[0044] In Fig. 9, a torque calculation unit 42 calculates the drive torque of the valve drive unit 3 based on drive parameters such as the rotation speed of the motor unit 33 detected by a rotation sensor 51 and the motor current value detected by a current sensor 53. The drive torque can be calculated according to a known method. For example, the drive torque can be calculated according to the following formula (1). Note that the coefficients in the following formula (1) are values ​​that can be obtained by experiment. Driving torque = coefficient × motor current value / motor rotation speed (1)

[0045] The leakage determination unit 43 determines the presence or absence of leakage between the seat member 23 and the valve body 22 based on the drive parameters of the valve drive unit 3. For example, in the configuration of Fig. 9, the seat leakage is determined based on the drive torque calculated by the torque calculation unit 42 and a predetermined threshold value.

[0046] Figure 11 shows the transition of the drive torque calculated from the drive parameters using a new seat material and a worn seat material. Figure 11 shows the case where the opening and closing time is 8.0 seconds and the differential pressure, which is the pressure difference between the upstream flow path and the downstream flow path, is zero. Note that the drive torque in the figure is a value calculated using the above formula (1) without using a torque sensor.

[0047] As shown in FIG. 11, the new seat member and the worn seat member behave in a similar manner, but the drive torque value during the period when the drive torque increases is smaller for the worn seat member. When the seat member sags or wears, the repulsive force of the seat member when the valve is closed decreases, so the drive torque becomes smaller than in the normal state. Based on this result, the leak determination unit 43 shown in FIG. 9 determines that a seat leak has occurred when the calculated drive torque is smaller than a predetermined threshold value. The predetermined threshold value can be set based on a correlation between the amount of seat leakage and the drive torque that has been obtained in advance by experiment.

[0048] On the other hand, if the fluid contains solid foreign matter such as powder or slurry, seat leakage may occur due to the foreign matter being caught. In the case of a foreign matter being caught, the closing operation of the valve becomes an overload, so it is considered that the driving torque becomes larger than normal. Therefore, by determining that a seat leakage has occurred when the calculated driving torque is smaller than a predetermined threshold value, it is possible to distinguish and detect seat leakage due to settling or wear, rather than seat leakage due to a foreign matter being caught.

[0049] Next, FIG. 12 shows the relationship between drive torque and differential pressure. FIG. 12(a) shows the results of examining the differential pressure using a new seat member, and FIG. 12(b) shows the results of examining the differential pressure using a worn seat member. As shown in each figure, the drive torque tends to be higher as the differential pressure increases. In this way, since the drive torque when the valve is closed changes depending on the differential pressure, when using a threshold value to determine seat leakage, it is preferable to set the threshold value according to the differential pressure. When comparing cases where the differential pressure is the same, the drive torque of the worn item is lower than that of the new item.

[0050] As another method of determination in the leakage determination unit 43, a method of determining that a seat leakage has occurred when the difference between the calculated drive torque and a past value (for example, the drive torque calculated when the valve was closed the previous time) becomes equal to or greater than a certain value can be adopted. For the past value, for example, the average value of the past 100 times can be used.

[0051] 9, the sheet leakage is judged based on the drive torque calculated by the torque calculation unit 42, but the leakage judgment may be performed based on a drive parameter other than the drive torque. For example, since the motor current value is almost correlated with the drive torque of the motor unit 33, the motor current value can be directly used for the leakage judgment.

[0052] Next, a process of detecting sheet leakage by the control unit 4 during a valve closing operation will be described. This detection process is repeatedly performed at predetermined time intervals.

[0053] Fig. 13 is a flowchart showing the processing procedure for sheet leakage detection. The processing from start to end in Fig. 13 is repeated at predetermined time intervals. First, in step S11, it is determined whether or not a command to close the valve (close command) has been input from a higher-level control device or the like. If step S11 is Yes, the process proceeds to step S12, and if step S11 is No, this process is temporarily terminated.

[0054] In step S12, it is determined whether or not the switching flag is OFF. As described later, the switching flag is turned ON after the valve body 22, which rotates at the first speed, rotates to a predetermined position. If step S12 is Yes, the process proceeds to step S13, where the motor unit 33 is driven. The valve body 22 rotates at the first speed toward the fully closed state by driving the motor unit 33. In step S14, drive parameters related to the drive of the motor unit 33 are acquired. Specifically, a motor current value and a motor rotation speed are acquired. In the following step S15, a drive torque is calculated based on the acquired motor current value and motor rotation speed.

[0055] In step S16, it is determined whether the driving torque is within the normal range. Specifically, it is determined whether the driving torque calculated in step S15 is between a predetermined upper threshold and a lower threshold. These thresholds are appropriately set according to the type and flow rate of the fluid flowing through the flow path. As shown in FIG. 11, in general, the driving torque is stable at a low value until it exceeds the rotation angle at which the valve body 22 contacts the seat member (for example, the rotation angle θ is 60 degrees). Therefore, if the driving torque suddenly increases and becomes equal to or exceeds the predetermined upper threshold, it is considered that an abnormality such as a foreign object being caught has occurred. If it is determined that the driving torque is not within the normal range (if step S16 is No), the process proceeds to step S26 and error processing is executed. As the error processing, an alarm is issued, an alarm lamp is turned on, or the like. Note that as the error processing, the driving of the motor unit may be stopped to interrupt the valve closing operation.

[0056] If step S16 is Yes, the process proceeds to step S17, where it is determined whether the valve element 22 has rotated to a predetermined position. Specifically, it is determined whether the rotation angle θ detected by the angle sensor 52 has reached a predetermined angle. If the valve element 22 has not reached the predetermined position (if step S17 is No), this process is temporarily terminated. Note that in FIG. 13, if step S17 is No, a loop may be provided in which the processes of steps S13 to S17 are repeatedly executed.

[0057] When the closing operation of the valve element 22 further progresses and the valve element rotates to a predetermined position (step S17: Yes), the switching flag is turned on (step S18), and this process is temporarily terminated.

[0058] If the switching flag is turned on and step S12 is negative, the process proceeds to step S19, where the valve element 22 is rotated at the second speed. This switches the rotation speed from the first speed to the second speed. In the following step S20, it is determined whether the valve element is in the fully closed position. Specifically, it is determined whether the rotation angle θ detected by the angle sensor 52 is 90 degrees. If step S20 is negative, the drive parameters are acquired (step S23), and the drive torque is calculated (step S24). The processes of steps S23 and S24 are the same as those of steps S14 and S15.

[0059] In step S25, it is determined whether the driving torque is within the normal range. Specifically, it is determined based on the driving torque calculated in step S24 and the predetermined upper and lower thresholds. Here, the relationship between the calculated value and each threshold is shown in FIG. 14. As shown in FIG. 14, the upper threshold is set higher than the driving torque in the normal state (for example, at the time of shipment), and the lower threshold is set lower than the driving torque in the normal state. Although the setting of each threshold is not particularly limited, the upper threshold is set, for example, 10% higher than the driving torque in the normal state, and the lower threshold is set, for example, 10% lower. In step S25 of FIG. 13, for example, it is determined whether the driving torque calculated at each rotation angle falls between the predetermined upper and lower thresholds at that rotation angle. If it is determined that the driving torque is outside the range between the two thresholds (if step S25 is No), the process proceeds to step S26 and error processing is executed.

[0060] If it is determined that the drive torque is within the normal range (if step S25 is Yes), this process is temporarily terminated. Then, if the valve closing operation proceeds while the drive torque remains within the normal range, the valve body 22 reaches the fully closed position, and step S20 is affirmative, the drive of the motor unit 33 is stopped (step S21), the switching flag is turned off (step S22), and the series of processes is terminated. Note that the portion that executes the processes of steps S13 and S19 corresponds to the speed control portion, the portion that executes the process of step S17 corresponds to the position determination portion, the portion that executes the process of step S24 corresponds to the torque calculation portion, and the portion that executes the process of step S25 corresponds to the leakage determination portion.

[0061] 13 shows the process in the control unit 4 during the valve closing operation, but the control method of the present invention is not limited to this. For example, the predetermined position determined in step S17 may be variable depending on the flow rate, viscosity, temperature, etc. of the fluid.

[0062] In FIG. 13, in the leak determination in step S25, it is determined whether the calculated drive torque is between the upper threshold and the lower threshold, but this is not limiting. For example, the leak determination may be performed using only a threshold set lower than the normal drive torque. As described above, when the seat member is worn or worn down, it is considered that the drive torque becomes smaller than the normal drive torque. Therefore, if the drive torque falls below this threshold, it can be determined that seat leakage has occurred.

[0063] In addition, in FIG. 13, sheet leakage is determined based on the drive torque while the valve disc is rotated at the second speed. That is, a configuration is shown in which the occurrence of sheet leakage is detected by the eccentric valve device 1, but sheet leakage can also be predicted with a similar configuration. In this case, for example, by setting the lower limit threshold used in step S25 higher than in the case of sheet leakage detection, it is possible to determine the stage immediately before sheet leakage occurs (signs of sheet leakage). Based on the determination result, it is possible to predict the timing of sheet leakage. It is also possible to determine the timing of sheet leakage from the transition of the drive torque calculated at any time. As a result, it is possible to detect the occurrence of sheet leakage in advance and issue an alarm.

[0064] FIG. 15 is a timing chart showing the flow when the valve body 22 transitions from a fully open state to a fully closed state. When a command to close the valve body is issued at time t1 in the fully open state, the motor unit starts and the valve closing operation starts at a first speed V1. As time passes, the rotation angle θ increases. At this time, the drive torque is stable at a low value. When the valve body rotates to a predetermined position at time t2, the rotation speed of the valve body 22 is switched to a second speed V2. The valve opening operation further progresses, and the drive torque increases as the seat member and the valve body come into contact with each other. When the valve body reaches a fully closed state at time t3, the motor unit stops and the valve closing operation is completed. Between time t2 and time t3, seat leakage is judged at any time based on the drive torque. The time required from time t1 to time t3 corresponds to the opening and closing time.

[0065] In the present invention, the manner in which the rotation speed of the valve disc is changed by the speed control unit is not limited to the manner in FIG. 15. For example, as shown in FIG. 16(a), a period (time t5 to time t6) in which the rotation of the valve disc is temporarily stopped may be provided between a period (time t4 to time t5) in which the valve disc is rotated at the first speed V1 and a period (time t6 to time t7) in which the valve disc is rotated at the second speed V2. In this case, when the valve disc rotates to a predetermined position, the motor unit stops at time t5 and the valve closing operation is temporarily stopped. After the temporary stop time has elapsed, the motor unit starts up and the valve closing operation is resumed at the second speed V2 (time t6). The time for which the valve disc is temporarily stopped can be set appropriately. In addition, it is preferable that the position where the valve disc is temporarily stopped is a predetermined position close to the seat member.

[0066] Also, as shown in Fig. 16(b), a period (time t9 to time t10) in which the valve body is rotated at a third speed V3 slower than the first speed V1 and faster than the second speed V2 may be provided between a period (time t8 to time t9) in which the valve body is rotated at the first speed V1 and a period (time t10 to time t11) in which the valve body is rotated at the second speed V2. In this case, the time in which the valve body is rotated at the third speed V3 can be set appropriately. Furthermore, a period in which the valve body is rotated at another speed may be added to the embodiment of Fig. 16(b).

[0067] In the above embodiment, a double eccentric valve has been described as an eccentric valve device according to the present invention. However, the present invention can also be applied to an eccentric valve that exhibits a change in drive torque similar to that of a double eccentric valve when the valve is opened and closed.

[0068] The eccentric valve device of the present invention is capable of detecting or predicting seat leakage caused by sagging or wear while shortening the opening and closing time of eccentric valves including double eccentric valves installed in the production process piping of a production factory, thereby enabling safe and efficient maintenance and reducing the overall loss of the production process. In addition, it is also possible to replace the valve before seat leakage occurs, which contributes to stable operation of the equipment and reduces the work involved in equipment maintenance and maintenance. [Explanation of symbols]

[0069] 1: Eccentric valve device 2: Valve mechanism 21: Valve box 211: Opening 212: Mounting hole 213: Pin groove 214:Dan section 22: Valve body 221: Valve section 222: Support part 223: Support part 23: Sheet material 231: Seat ring 232: Rubber ring 24: Support member 25: Pin 3: Valve drive section 31: Power supply circuit section 32: Motor circuit section 33: Motor section 34: Reducer 35: Valve stem 4: Control unit 41: Speed ​​control section 42: Torque calculation section 43: Leak detection section 51: Rotation sensor 52: Angle sensor 53: Current sensor

Claims

1. An eccentric valve device for controlling blocking or opening of a flow path in a pipe, The eccentric valve device includes a substantially cylindrical valve box having an opening communicating with the flow path, a ring-shaped seat member attached around the opening in the valve box, a valve body rotatably provided in the valve box and blocking the flow path by being pressed against the seat member, a valve drive unit that rotates the valve body, and a control unit that controls the drive of the valve drive unit, The valve body is structured so as not to come into contact with the seat member in a fully open state, and to come into contact with the seat member in a fully closed state, the control unit has a speed control unit that changes a rotation speed of the valve element during a process of the valve element rotating from the fully open state to the fully closed state, and a leakage determination unit that determines the presence or absence of leakage between the seat member and the valve element based on a drive parameter of the valve drive unit, the speed control unit rotates the valve body from the fully open state at a first speed, and then changes the rotation speed to a second speed slower than the first speed to rotate the valve body to the fully closed state, and rotates the valve body at the second speed from a predetermined position where the valve body is close to the seat member to the fully closed state, wherein the predetermined position is a position where the valve body does not contact the seat member and is a position where a gap between the valve body and the seat member can be narrowed to increase the flow rate of the fluid.

2. the control unit has a torque calculation unit that calculates a drive torque of the valve drive unit based on a motor current value and a motor rotation speed of the electric motor that is the valve drive unit, as the drive parameters; 2. The eccentric valve device according to claim 1, wherein the leakage determination unit determines that a leakage has occurred between the seat member and the valve body when the drive torque is smaller than a predetermined threshold value while the valve body is rotating at the second speed.

3. 3. The eccentric valve device according to claim 1, wherein the time required for the valve body to change from the fully open state to the fully closed state is within 3.0 seconds.

4. 4. The eccentric valve device according to claim 1, wherein the valve drive unit is an electric motor that is capable of rotating the valve body by inertia even after the supply of current thereto is stopped.

5. A method for controlling an eccentric valve device that controls blocking or opening of a flow path in a pipe, comprising: The eccentric valve device includes a substantially cylindrical valve box having an opening communicating with the flow path, a ring-shaped seat member attached around the opening in the valve box, a valve body rotatably provided in the valve box and configured to block the flow path by being pressed against the seat member, and a valve drive unit configured to rotate the valve body. The valve body is structured so as not to come into contact with the seat member in a fully open state, and to come into contact with the seat member in a fully closed state, The control method includes a step of rotating the valve disc at a first speed during a process in which the valve disc rotates from the fully open state to the fully closed state, and a step of determining the presence or absence of leakage between the seat member and the valve disc based on a drive parameter of the valve drive unit while the valve disc is rotated at a second speed slower than the first speed, a step of rotating the valve body from the fully open state at a first speed, changing the rotation speed to a second speed slower than the first speed to rotate the valve body to the fully closed state, and rotating the valve body at the second speed from a predetermined position where the valve body is close to the seat member to the fully closed state, wherein the predetermined position is a position where the valve body does not contact the seat member and where a gap between the valve body and the seat member can be narrowed to increase the flow rate of the fluid.

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